Abstract
In order to effectively extract specific flavonoids with high biological activity from onionskin, NaNO2- Al(NO3)3-NaOH coloration method, spectrophotometry and MTT method were adopted to study the yield rate and content of flavonoids obtained from alcohol water and alkali water extraction processes, the antioxidant activities and the in vitro effects on K562 cell viability. The results indicated that yield rates of flavonoids obtained by alcohol water and alkali water extraction methods were 3.76% and 2.37%, and solid flavonoids contents were 42.20% and 76.21% respectively; under the same concentration of total flavonoids, alkali water extract has weaker effect on removing superoxide anions and DPPH • radicals, whereas they have similar effect on removing nitrite and hydroxyl free radicals; in the test concentration range (40 ∼ 200 µg / mL), they have similar effect on inhibiting the proliferation activity of K562 cells; the maximum inhibition rate of flavonoids obtained by alkali water extraction method is 77.71%, while maximum inhibition rate of flavonoid obtained by alcohol water extraction method is 70.64%. Both the flavonoids obtained from onionskins by alcohol water extraction method and alkali water extraction method have good biological activity. The alkali water extraction method is simple and without any alcohol consumption, and the product purity is high. Although the yield rate and certain biological activity of flavonoids obtained by alkali water extraction method are lower than those obtained by alcohol water extraction method, it still has certain significance in industrial production.
Highlights
INTRODUCTIONFlavonoids refer to the compounds that exist in nature and have 2-phenyl-chromone (flavone) structure
Flavonoids refer to the compounds that exist in nature and have 2-phenyl-chromone structure
Radicals, whereas they have similar effect on removing nitrite and hydroxyl free radicals; in the test concentration range (40 ~ 200 μg / mL), they have similar effect on inhibiting the proliferation activity of K562 cells; the maximum inhibition rate of flavonoids obtained by alkali water extraction method is 77.71%, while maximum inhibition rate of flavonoid obtained by alcohol water extraction method is 70.64%
Summary
Flavonoids refer to the compounds that exist in nature and have 2-phenyl-chromone (flavone) structure. The results indicate that all these flavonoids have different effects on inhibiting the proliferation of these cancer cells, and have no significant cytotoxicity [3]. There are very few studies on the biological activity of flavonoids obtained from onionskin. Chen Fengxiu, et al found that the flavonoids in onion can significantly inhibit the proliferation of colon cancer HCT116 cells in vitro and induce their apoptosis [4]. Chen Jia studied the antioxidant activity in vitro of flavonoids obtained from onionskin by enzyme-assisted extraction method [5]. The paper studies the antioxidant activity of extracts derived by different methods and the in vitro inhibition on the proliferation viability of K562K562 leukemia cell, in order to provide basis for choosing an effective method to extract flavonoids with high biological activity The optimum conditions for these two methods: alcohol water extraction method: 50% ethanol soaking, extraction for two times, extraction temperature is 71.6~73.8 °C, extraction time is 2.0~2.2 h, the ratio of liquid to solid is 30.1~34.2: 1 [6]; alkali water extraction method: pH 11 NaOH solution soaking, extraction for two times, extraction temperature is 83.0 °C ~ 84.0°C, extraction time is 1.9~2.0 h, the ratio of liquid to solid is 34.1~38.1: 1. The paper studies the antioxidant activity of extracts derived by different methods and the in vitro inhibition on the proliferation viability of K562K562 leukemia cell, in order to provide basis for choosing an effective method to extract flavonoids with high biological activity
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